Patterns of colonization by Pseudomonas aeruginosa in intubated patients: a 3-year prospective study of 1,607 isolates using pulsed-field gel electrophoresis with implications for prevention of ventilator-associated pneumonia.

OBJECTIVE: To identify routes and patterns of colonization with Pseudomonas aeruginosa in intubated patients to design strategies of prevention for respiratory infection. DESIGN AND
SETTING: Prospective and observational study in the 16-bed intensive care unit of a teaching hospital. PATIENTS AND PARTICIPANTS: Ninety-eight intubated patients were investigated over a 3-year period. Those ventilated less than 72 h were excluded. MEASUREMENTS AND
RESULTS: Samples from the tap water from each patient's room, stomach, oropharynx, subglottic secretions, trachea, and rectum were collected when the patient was intubated, and then three times per week. Pulsed-field gel electrophoresis was performed to type the strains. We identified 1,607 isolates pertaining to 35 different pulsotypes. Overall 54.2% of patients presented colonization, and tracheal colonization was present in 30.5%. Ten patients had colonization at intubation, and four of these developed ventilator-associated pneumonia (VAP) after a mean of 4+/-2 days. ICU-acquired colonization occurred in 31 patients, and 4 of these developed VAP after a median of 10+/-5 days. P. aeruginosa was isolated from the room's tap water in 62.4% of samples. More than 90% of tap water samples had pulsotypes 1 and 2, which were frequently isolated in the stomach (59%) but were only rarely associated with VAP.
CONCLUSIONS: Although colonization/infection with P. aeruginosa in intubated patients tends to be endogenous, exogenous sources should not be ruled out. A combination of early identification (and eradication) of airways colonization by P. aeruginosa plus infection control measures targeted to reduce cross-contamination should be the basis to prevent pulmonary infection.